The publisher is driven through a real LocalParticipant whose device and
signalling calls are faked, so that LiveKit's own pending-publication
bookkeeping is part of what is tested: the cases ported from Element
Call's Publisher tests (one permission prompt for both devices, nothing
created while muted, the upstream held back until the member publishes,
a mute that lands while the track is still being created) plus the
publish, unpublish and destroy paths.
The local media runs on a fake connection map: publishing before and
after the connection exists, republishing on a new connection, mutes
remembered across connections, the first publish error kept, and the
output device applied to the current room and the ones to come.
The participation runs on a fake media backend: the join options, the
state machine through connecting, connected, reconnecting, failed and
left, publishing only while joined, the delayed leave delegation, the
member ids per mode, the key replay and the data channel's sender check.
